1. Field of the Invention
The present invention relates to a vehicle seatback and to a vehicle seat provided with a vehicle seatback.
2. Description of the Related Art
As a seatback for a vehicle seat, a known seatback is provided with a seatback frame, and a plate body attached to the seatback frame for supporting the back of an occupant seated in the vehicle seat (for example Japanese Patent Application Laid-Open (JP-A) No, 2009-101137). The plate body described in JP-A No. 2009-101137 is formed with an opening extending along the seatback height direction. The opening is formed in a position corresponding to the thoracic vertebrae of an occupant seated in the vehicle seat. Due to the opening, reaction force acting on the thoracic vertebrae of the occupant is reduced when the back of the occupant is pressed against the plate body, thereby improving seating comfort of the occupant.
However, with the seatback described in JP-A No. 2009-101137, when, for example, there is a collision from the vehicle rear by another vehicle or the like (rear impact) and a load of a specific value or greater acts on the occupant due to inertia, the lower neck region of the occupant (cervical vertebrae) are pressed against the seatback upper frame portion of the seatback provided above the plate body. Since generally the seatback upper frame portion here is configured from steel tubing, such as a pipe or the like, reaction force acting on the lower neck region of the occupant is concentrated, increasing strain on the lower neck region.